The Sun, Skin, and Nitric Oxide

Nitric Oxide, or NO is an incredibly simple molecule, a nitrogen and an oxygen that are stuck together with 2 bonds. NO is very important for many things, most importantly it lowers blood pressure. Healthy human skin tissue contains significant quantities of nitrite. Stores of nitrites can be turned into nitric oxide. Every cell type in human skin is able to produce nitric oxide by several mechanisms. Dietary nitrate represents an important source of cutaneous nitric oxide. Green leafy vegetables, beetroots, lettuce have a lot of these nitrites. Also carnivorous sources of arginine result in stores of nitric oxide; turkey, pork and chicken are good sources. Supplements such as arginine and citrulline may also be sources of dietary nitrate.

Nature has a reason for everything it does. Sunlight exposure increases skin production of nitric oxide, which can dilate the 60,000 miles of blood vessels we have in our body, and improve blood flow. Ultraviolet light from the sun, specifically UVA, is what triggers the increase in NO from the skin. It’s likely that the coronary arteries are dilated by NO derived from the skin as well. Think about this, we have over 60,000 miles of blood vessels and endothelial cells (350m2), and our skin has many ways to produce NO. And it has been shown that in humans exposed to proper sunlight or sunlamps for 30 minutes, that the UV rays produces a rise in circulating NO as well as a dilation in blood vessels resulting in decreased blood pressure. This improves cardiovascular health.

Our internal impulses to migrate south during the winter are not so far fetched after all. There is actually some truth to the North – South health divide. Living at the equator releases a lot of NO; whereas living in Scotland in the winter probably releases small amounts of NO. Australians have about a third less heart disease than do people from Scotland or some parts of Britain. Why is this? The Australians have less deaths from heart attacks, heart failure, less strokes and are a healthier bunch in general. It’s not just Australia that has better health than Britain, but there are differences within in Britain itself. There is actually a difference in CVD mortality whether you live in London or Glasgow and some researchers think it has to do with NO production from the sun. Even after controlling for things like smoking, deep-fried fish and chips, social class, and diet, the mortality rate increases the further north you travel. It should be noted that vitamin D is also extremely important in nitric oxide production from UV light exposure (related article on Vitamin D and Statins).